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Life’s Molecules
Carbohydrates
Carbohydrates
Monosaccharide (Glucose)
Carbohydrates
Polysaccharide (glycogen)
Carbohydrates
Polysaccharides (amylose and cellulose)
Lipids
Lipids
Three fatty acid tails
glycerol
Triglyceride
Lipids
Triglycerides are the most common fats in food.
Lipids
Stearic acid: saturated
Oleic acid: unsaturated
Linoleic acid: polyunsaturated
Saturated and unsaturated fatty acids
Lipids
Phospholipid
Lipids
Phospholipids arrange themselves as a bilayer in water.
The hydrophilic heads face out, the hydrophobic
tails face inward.
Lipids
Lipids are hydrophobic. Plant leaves are coated with
waxes to keep water inside the plant.
Proteins
Amino group
Carboxyl group
R group
One of 20 amino acids (valine). Amino acids vary by
the “R” group they contain.
Proteins
Amino acids are linked by peptide bonds
to form polypeptides
Proteins
A bit of the primary structure (amino acid sequence)
of globin.
Protein, Secondary structure
A globin molecule. The arrangement of amino acids in
this molecule encourages formation of hydrogen bonds.
These bonds cause the molecule to coil helically, giving
rise to its secondary structure (the purple portion).
Protein, Tertiary structure
Interactions between R groups at various areas along
the spiral cause it to fold and bend. This gives the
molecule its tertiary structure (the green portion).
Protein, Quaternary structure
Hemoglobin is an example of the fourth level of
protein structure (quaternary structure). In all proteins
at this level of organization, two or more polypeptide
chains are joined together. Hemoglobin has four
polypeptide chains.
Proteins
To summarize the four levels of protein structure:
1. Primary structure is the sequence of amino acids in
a polypeptide chain.
2. Secondary structure is the coiled or extended shape
that the chain assumes owing to hydrogen bonds at
short intervals along the chain.
3. Tertiary structure refers to further folding of a coiled
chain owing to bend-producing amino acids and
interactions among R groups far apart on the chain.
4. Quaternary structure is the linkage of two or more
polypeptide chains by hydrogen bonds and other
interactions.
Nucleic Acids
Nucleic Acids
Nucleotide
Nucleic Acids
DNA: nucleotides bonded by hydrogen bonds
Nucleic Acids
Nitrogen-containing base
3 phosphate groups
5 carbon sugar
ATP (adenosine triphosphate), the energy
currency of every cell
Nucleic Acids
ADP (adenosine diphosphate). When ATP releases its
stored energy, it is converted to ADP + Pi
Enzymes and Reactions
• An enzyme is a protein that accelerates a chemical
reaction.
• They may combine, separate or rearrange molecules.
• The enzyme and its substrate have a key and lock type
of relationship, one enzyme usually only works with one
or two molecules.
Terminology
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Substrate
Active site
Coenzyme
Metabolic pathway
Metabolism
Activation Energy
Endergonic
Exergonic
Regulation of Enzyme Activity
1. The amount of substrate present regulates the
reaction
2. The active site of the enzyme can be blocked by a
molecule similar to the substrate. This is called
Competitive Inhibition.
3. Allosteric Regulation, the regulation of enzyme
activity by means of a molecule binding to a site
other than the active site.
- Can decrease or increase enzyme activity.
Lowering the Activation Energy of a Reaction
Lowering the Activation Energy of a Reaction
Electron Carriers transport electrons
from one molecule to another.
ATP / ADP cycle
Oxidation – Reduction Reactions
OIL RIG
Respiration: Deriving energy from food
Aerobic respiration
C6H12O6 + 6O2 + 36 ADP + 36 Pi -------->
6CO2 + 6H20 + 36ATP
Glucose: the starting point for cellular respiration
Three stages of aerobic respiration
Where does it
happen?
Step 1
Glycolysis
Step 1.5
Conversion
of Pyruvic
acid to
Acetyl CoA
Step 2
Kreb’s
Cycle
Step 3
Electron
Transport Cycle
How other foods fit into
Cellular respiration
Anaerobic Respiration or Fermentation
• Far less efficient than Cellular Respiration with only
2 ATP generated per Glucose.
• By products are varied : alcohol, lactic acid, acetic acid
Anaerobic respiration or alcoholic fermentation
Anaerobic respiration or lactic acid fermentation
Photosynthesis
The process by which certain groups of organisms capture energy from
sunlight and convert this solar energy into chemical energy that is
initially stored as a carbohydrate.
sunlight
6H2O + 6CO2 ------------> 6O2 + C6H12O6
Two steps in photosynthesis
Photosynthetic terminology
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Leaf, petiole, blade
Epidermis, mesophyll cells, stomata
Chloroplast, vacuole, cell wall
Thylakoids, stroma, granum, inner/outer membrane
Thylakoid membrane, thylakoid compartment
Chlorophyll a, accessory pigments
Light wavelengths absorbed by chlorophylls
Plants reflect green light and absorbs the red and blue light.
Photosystem
• An organized complex of molecules within a thylakoid
membrane, that collects solar energy and transforms it
into chemical energy.
• Pigment molecules and accessory pigments serve as
‘antennae’ and absorb energy from the sun and pass it
onto the reaction center ( a couple of chlorophyll a
molecules).
– Electrons are moved in two ways
• Physically transferred to the electron acceptor
• Metaphorically up the energy hill
The chlorophyll molecules lose electrons to the primary electron
acceptor.
This is a redox reaction
• This is the photo of photosynthesis
• Photosystem II collects solar energy, its electron moves
to another part of the reaction center, the primary
electron acceptor.
• This leaves an energy ‘hole’ which is filled by splitting
water into 2 H+ and ½ O2. (Oh, that’s where Oxygen comes from!)
When the energized electrons fall they release energy
that is captured as they are transferred through a series
of electron transport molecules.
• They then arrive at Photosystem I where they are again
boosted by light energy. Again the electrons pass along
an electron transport chain and at the end are received
by NADP+ where they proceed to the dark reactions.
The light reactions.
Physical movement of electrons
• Started out in the water of the thylakoid
compartment.
• Moved into and through the thylakoid membrane
• End in stroma, attached to NADPH
• ATP that is produced in the light reactions is
used in the dark reactions to produce food.
The Dark Side
• Also called the Calvin Cycle or C3 Cycle.
• This is the synthesis of photosynthesis.
• A process by which CO2 is taken from the
atmosphere and joined to a sugar (energized)
and stored as a carbohydrate.
• NADPH and ATP are located in the stroma
where there Calvin Cycle takes place.
• Fixation, the process where a gas is
incorporated into an organic molecule.
• The starting point is RuBP or ribulose
biphosphate a type of sugar.
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Bring together CO2 and RuBP by enzyme rubisco
Energize the sugar
Exit of the product
Regeneration of RuBP
Start over
The Calvin Cycle
The dark reactions
Summary
• Solar energy is converted to chemical energy in
the thylakoids and stored as ATP, NADPH
• Water is required
• Oxygen is a byproduct
• Stored chemical energy is used in the Calvin
Cycle (in the stroma) to produce a high-energy
sugar from CO2 (from the atmosphere, in thru
the stromata) and RuBP.
• Dinner is served!
A summary of photosynthesis